There are many types of vehicle security systems or vehicle anti-theft systems in use today for preventing unauthorized entry into, and operation of, a vehicle. A system such as this usually includes some means for disabling the vehicle when the system is armed or rendered operative and some kind of an alarm which sounds when attempts are made to enter the vehicle or to lift the vehicle's hood or to tamper with the security system. In systems designed for incorporation into vehicles with power door locks, the system may also include a module for automatically actuating the door locks when the vehicle is armed or rendered operative.
Some vehicle security systems are so-called active systems in the sense that the system is armed and disarmed by actuation of a key switch outside the vehicle. Some contemporary active systems use coded radio frequency (RF) transmitters and receivers to arm and disarm the system. An example of this type of arrangement is disclosed in U.S. Pat. No. 3,703,714.
Other systems are denominated passive systems because they become armed or set automatically after the operator leaves the vehicle. For example, some passive systems become armed a selected time after the ignition has been turned off. Usually such systems require the installation of a conductor from the security system to the ignition circuitry to sense whether or not the ignition is turned on. Other systems are set automatically after all of the vehicle doors have been closed. The trouble with these prior passive systems is that they fail to take into consideration whether or not there are any passengers in the vehicle at the time the system is armed. Obviously, if a person or pet happens to be in the car when the system becomes armed, any motion of that person or pet would set off the alarm. Also, if the system includes an automatic door lock feature, the arming of the system may often result in the locking of the doors, making it more difficult for a less competent passenger such as a small child or an aged or infirmed adult to escape from the vehicle in an emergency situation.
Another problem with prior vehicle security systems is that there is no convenient and secure arrangement for overriding the system in the event that the arm/disarm transmitter becomes inoperative or lost. While these hand held transmitters are very convenient, they do have problems, to wit: their batteries wear out, they become wet, they are sometimes subject to external electrical interference, etc.
The common provision for allowing the vehicle operator to override the security system without a transmitter is to provide a "hidden" override or valet switch in the vehicle. It is the universal procedure to require the ignition switch and the override switch to be ON in order to disarm the security system. The accepted theory is that a thief cannot disable the system even if he finds the override switch because he does not have the key to the ignition switch. However, this completely ignores the fact that the thief can easily penetrate the vehicle's steering column and disable the ignition switch. After doing that, he simply feels around under the dash or elsewhere to find the hidden override switch. The switch wiring may also lead him to the alarm control module enabling him to completely disable the security system. Thus, the presence of the hidden override switch actually undoes all the security ostensibly provided by the carefully coded alarm system transmitter. In actuality, then, the value of an override switch depends upon the specific vehicle model and the ability of the installer to adequately hide the switch. Examples of such conventional systems with override or valet switches are disclosed in U.S. Pat. Nos. 5,049,867 and 5,079,538.